You can re-use redsn0w v0.8 we released a few weeks ago to jailbreak today’s 3.0.1 update. Just let iTunes update or restore you to official 3.0.1 then run redsn0w. The only “trick” is that when redsn0w asks you to identify the IPSW used, point it at the 3.0 IPSW instead of the 3.0.1 one. After the jailbreak, reinstall ultrasn0w 0.9 if you need the unlock.

There’s nothing new in iPhone OS 3.0.1. It only comes with a patch to the SMS flaw that allows hackers to take control of your iPhone.